Process for production of starch sugars

Abstract

The present invention provides a process for production of starch sugars, wherein starch is subjected to liquefaction and saccharification to prepare a mixture containing 10-50% by weight, based on the total solid content, of glucose and 30-50% by weight, also based on the total solid content, of maltose and the mixture is concentrated so as to have a total solid content of 40-70% by weight; and the resulting mixture is subjected to component separation using a chromatographic separator of simulated moving bed type capable of fractionating the mixture into at least three fractions, to produce a glucose fraction with a glucose purity of at least 97% by weight, a maltose fraction with a maltose purity of at least 80% by weight and a high-purity oligosaccharide fraction at a high efficiency in one operation. In the process, no strict control is required for the enzymatic reactions taking place in the liquefaction and saccharification of starch, and all the fractions obtained by the chromatographic fractionation can be made into marketable products.

What is claimed is: 
     
       1. A process for production of starch sugars, wherein an aqueous starch sugars solution produced from starch is subjected to chromatographic fractionation to produce a glucose fraction with a glucose purity of at least 97% by weight, a maltose fraction with a maltose purity of at least 80% by weight and an oligosaccharide fraction in one operation, which process uses, as a feed to be fractionated, an aqueous starch sugars solution prepared by allowing a liquefaction enzyme to act on starch to produce liquefied starch, allowing saccharification enzymes for producing glucose and maltose to act on the liquefied starch to produce an aqueous starch sugars solution containing 10-50% by weight, based on the total solid content, of glucose, 30-50% by weight, also based on the total solid content, of maltose and oligosaccharides having molecular weights the same as or larger than maltotriose molecular weight, and concentrating the aqueous starch sugars solution so as to have a total solid content of 40-70% by weight, and which process further employs, for fractionation of a feed to be fractionated, a chromatographic separator capable of fractionating the feed into three or more fractions, constituted in such a way that a plurality of columns packed with an adsorbent, which is a cation exchange resin, are connected by fluid paths so as to form an endless serial circulation channel, that at each connection point between the columns, the feeding of an eluant and the withdrawal of an eluate fraction can be conducted, that a shutoff valve is provided at a particular position of the circulation channel and that a feed feeding path is connected with the circulation channel just downstream of the shutoff valve, the operation of said chromatographic separator being comprised of a first step of closing the shutoff valve, feeding a feed or a feed and an eluant and simultaneously withdrawing a maltose fraction or a maltose fraction and an oligosaccharide fraction, and a second step of opening the shutoff valve, feeding the eluant alone without suppyling the feed and simultaneously withdrawing an oligossacharide fraction and a glucose fraction while sequentially shifting the position for feeding the eluant and the positions for withdrawing the oligosaccharide fraction and the glucose fraction toward the downstream side of the circulation channel, thus the first and second steps accomplishing the chromatographic fractionation of said aqueous starch sugars solution as feed into at least the following three fractions: a. a glucose fraction wherein the glucose is enriched to a purity of at least 97% by weight,   b. a maltose fraction wherein the maltose is enriched to a purity of at least 80% by weight, and   c. an oligosaccharide fraction wherein the oligosaccharides having molecular weights the same as or larger than maltotriose molecular weight are enriched.   
     
     
       2. A process for production of starch sugars according to claim 1, wherein in the first step the maltose fraction is withdrawn in two fractions of a maltose fraction wherein maltose is enriched, and a mixed fraction of glucose and maltose, with the maltose fraction withdrawn earlier and the mixed fraction withdrawn later, thus the first and second steps accomplishing the chromatographic fractionation of the aqueous starch sugars solution as feed into the following four fractions: a. a glucose fraction wherein the glucose is enriched to a purity of at least 97% by weight,   b. a maltose fraction wherein the maltose is enriched to a purity of at least 80% by weight,   b'. a mixed fraction of glucose and maltose, and   c. an oligosaccharide fraction wherein the oligosaccharides having molecular weights the same as or larger than maltotriose molecular weight are enriched.   
     
     
       3. A process for production of starch sugars according to claim 1 or 2, wherein after the chromatographic fractionation, the glucose fraction "a" and the maltose fraction "b" are purified and concentrated independently to obtain a glucose product and a maltose product, respectively. 
     
     
       4. A process for production of starch sugars according to claim 1 or 2, wherein after the chromatographic fractionation, the glucose fraction "a", the maltose fraction "b" and the oligosaccharide fraction "c" are purified and concentrated independently to obtain a glucose product, a maltose product and an oligosaccharide-rich syrup product, respectively. 
     
     
       5. A process for production of starch sugars according to claim 2, wherein after the chromatographic fractionation, the glucose fraction "a" and the maltose fraction "b" are purified and concentrated independently to obtain a glucose product and a maltose product, respectively, and the mixed fraction "b'" and the oligosaccharide fraction "c" are mixed, purified and concentrated to obtain a maltose-rich syrup product. 
     
     
       6. A process for production of starch sugars according to claim 1, wherein between the saccharification of the liquefied starch and the concentration of the resulting aqueous starch sugars solution, the aqueous starch sugars solution is subjected to refining steps of filtration for removal of oils, fats, proteins, suspended solids and other impurities, and deionization or softening. 
     
     
       7. A process for production of starch sugars according to claim 1, wherein the cation exchange resin as adsorbent is in the Na form or the K form and the eluant is water. 
     
     
       8. A process for production of starch sugars according to claim 1, wherein the saccharification of the liquefied starch is conducted in one step by allowing a saccharification enzyme for producing glucose and a saccharification enzyme for producing maltose to simultaneously act on the liquefied starch.